Currently, in the field of wireless networks, the rapid growth of wireless local area network (WLAN) has increasing demands on the WLAN applications. The Institute of Electrical and Electronics Engineers industry specifications IEEE802.11 group has defined a series of standards 802.11a/b/g/n, and subsequently other task groups appeared and were dedicated to developing specifications for improving the 802.11 technology. For example, the 802.11ah task group mainly work on below 1 GHz unlicensed bands.
In the WLAN, one access point (AP) and a number of non-AP Stations associated with the access point form into a Basic Service Set (BSS). As shown in FIG. 1, the AP1 and the STA1 consist into a BSS, and the AP2 and the STA2-STA4 consist into another BSS. When two BSS use the same channel and their signal coverage is overlapping, the two BSSs are each other's overlapping BSS (OBSS). In this spatial reuse, the WLAN uses Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) as the basic mechanism of channel access to intercept carriers before transmission and have a random backoff function, namely, it only transmits data when confirming that the channel is idle; in addition, in order to perform multiple frame exchanges, the transmission/reception parties can reserve one time period of Transmission Opportunity (TXOP) to transmit frames in order to avoid the transmission collision.
For example, as shown in FIG. 2, assuming that the AP1 wins the channel and transmits radio frames to the STA1, before transmitting the data frames, the AP1 at first initiates and transmits a Request to send (RTS) frame to the STA1 to reserve a channel, and it carries channel reservation duration information in the RTS; the STA1 responds a clear to send (CTS) frame to the AP1 to confirm the channel reservation, wherein the CTS also carries the channel reservation duration information, and the Duration information indicates that the reservation is finished at the end of TXOP. Other intercepting stations that receive the radio frame carrying the Duration information set one network allocation vector (NAV) stored by themselves, and the value of the NAV is the maximum value of the abovementioned received Duration information, within the duration indicated by the NAV, even though the physical carrier is detected as idle, the intercepting station will not send data.
The abovementioned relevant time reservation and NAV mechanism are called a virtual carrier sensing mechanism. In addition to the NAV mechanism mentioned above, the related art also defines a virtual carrier sensing mechanism using Response Indication Deferral (RID), and the radio frame that is currently being sent carries the frame type of the radio frame to be sent next, the intercepting station selects a defer time to update the value of RID according to the frame type indicated by the radio frame that is currently being sent, and the station can only contend to send when the timer of RID is 0.
In the case of using the beamforming to perform sector transmission, the related art proposes a spatial orthogonal transmission solution, generally comprising: when the intercepting station (such as the station or access point in the OBSS) determines that the sector beam transmission of current transmission and reception stations is spatially orthogonal with the data transmission to be carried out by itself, the intercepting station may cancel the previously set reservation time for virtual carrier sensing and initiate the data transmission, taking the FIG. 1 for example, assuming that the AP1 and the STA1 at first send omnidirectional radio frames or signals, for example, the RTS/CTS establishes a connection and reserves the TXOP to protect the data transmission, and then they use the beam aligned with each other to perform data transmission within the TXOP, and the AP2 or the STA3 receives omnidirectional signals from the AP1 and/or the STA1, and updates the NAV and the RID; however, the AP2 or the STA3 cannot detect that the AP1 and STA1 aligns to the sector beam with each other, then the AP2 and the STA3 can consider that their own transmissions are spatially orthogonal with the beam transmissions of the AP1 and the STA1, then the AP2 and the STA3 reset the NAV and the RID and trigger their own frame transmissions.
As an optional feature, the related sector beam transmission makes different stations have the problem of access fairness. Taking what is shown in FIG. 3 and FIG. 1 as an example, assume that the AP1 and the STA1 use the sector transmission mechanism, the AP2, the STA3 and the STA5 have the sectorization capability of determining a spatial orthogonality and triggering a transmission, and the STA4 does not have such capability; in the network structure shown in FIG. 1, the AP2 and the STA3 begin to contend to transmit when the AP1 and the STA1 use the sector beam to transmit, i.e., after the time point t1; although the STA5 has the sectorization capability, it is able to detect the sector transmission between the AP1 and the STA1, so that it has to wait until after the end of the TXOP, i.e., after the time point t2, to start contention; the STA4 does not have the sectorization capability, according to the traditional mechanism, it has to wait until after the time point t2 to contend for the channel. Using the spatial orthogonal reuse to perform wireless resource sharing should guarantee that the access or transmission of other stations that do not perform the spatial orthogonal reuse are not affected, namely the transmission of the AP2 and the STA3 in the abovementioned scenario should not affect the access of the other intercepting station. However, the related art does not define access rules for the AP2 and the STA3, the transmission between the AP2 and the STA3 may exceed the sector beam transmission duration, that is, the time point t2, shown in FIG. 3, then in fact the intercepting station such as the STA4 cannot start to contend at the time point t2 and has to wait until the transmission of the AP2 and the STA3 ends to contend for the channel, and while waiting for the transmission of the AP2 and STA3 to end, the AP1 and the STA1 probably use the spatial orthogonality to start a new transmission, and there is no doubt that this is very unfavorable and unfair for channel access of stations such as the STA4 or the STA5, and it also affects the effectiveness of data transmission of such type of stations.